Business Segment Information (Financial Information By Reportable Segment) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2018 USD ($)	Jul. 01, 2017 USD ($)	Jun. 30, 2018 USD ($) segment	Jul. 01, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment			2
Total revenue	$ 194,668	$ 193,764	$ 580,153	$ 586,467
Total income from operations	16,264	16,617	49,371	42,319
Test
Segment Reporting Information [Line Items]
Total revenue	116,055	124,359	344,496	379,325
Total income from operations	3,873	8,709	12,777	26,792
Sensors
Segment Reporting Information [Line Items]
Total revenue	79,000	69,405	236,501	207,142
Total income from operations	12,398	7,908	36,623	15,527
Intersegment Eliminations
Segment Reporting Information [Line Items]
Total revenue	(387)	0	(844)	0
Total income from operations	$ (7)	$ 0	$ (29)	$ 0